Detailed geochemical assessment & indexing of shallow groundwater resources in metropolitan city of Nagpur (western Maharashtra, India) with potential health risk assessment of nitrate enriched groundwater for sustainable development

Abstract

Identification of complex processes controlling the groundwater chemistry and the indexing of urban groundwater for drinking were carried out with special emphasis on health risk associated with nitrate contamination in the urban areas of Nagpur City in western India. The hydrochemical facies of forty-seven samples collected from shallow aquifers were of Ca–HCO3 and mixed Ca–Na–HCO3 type indicating a transition from pure recharge water to mixed type water. 75% of the samples were very hard water. Geochemical signatures evaluated from the Na+-Cl− plot, Na+:Na+ + Cl−, Ca2+ + Mg2+ vs. HCO3− + SO42− plot, (Na++ K+ - Cl−)/(Na++ K+ - Cl− + Ca2+), Ca2+/Na+ vs. Mg2+/Na+, SO42−/Cl− signposted the collective contribution of calcite, dolomite, silicate, and gypsum weathering on groundwater geochemistry. The dominancy of cation exchange followed by reverse ion exchange, anthropogenic inputs, and mineral dissolution are resolved based on bivariate plots. The supersaturated thermodynamic states of calcite and dolomite minerals played a major factor for low Ca2+ in some samples. Nitrate higher than the drinking-water thresholds of 50 mg/L (as per WHO) in around 51.1% of the samples reflected the consequences of urbanization on shallow aquifers. The EWQI method ranked 74.5% of the urban groundwater as moderately suitable and remaining samples are not suitable for drinking. The non-carcinogenic risk (HI Total) were computed as 1.82, 2.16, and 2.47 for an adult male, adult female, and children of Nagpur urban region. The non-carcinogenic risk was higher in children as compared to the adult residents. The noteworthy finding of the study may help in building effective policies and enhancing individual cooperation for the sustainable development of groundwater reservoirs in this region.